A virtual machine operating system is well known today. It comprises a common base portion and separate user portions that all run on a physical computer. In an IBM VM/ESA operating system and subsequent IBM z/VM operating system, the common base portion is called the Control Program (“CP”) and each user portion is called a virtual machine or guest. Each virtual machine is a logical partition of physical resources of the computer. A guest operating system runs on each virtual machine, and the virtual machine appears to the guest operating system as a real computer. Many applications can run on each guest operating system and its virtual machine. Applications running on different virtual machines can communicate with each other through the common base portion. The communication may be in the form of messages conveyed by a service such as IUCV, which is based on IBM proprietary protocols. The IUCV service allows an application in one virtual machine to receive data from a storage buffer belonging to another virtual machine. IUCV does not result from any specific hardware architecture, so both applications must be programmed to use IUCV protocol. The IUCV service is further described in the publication entitled “z/VM V4R3.0 CP Programming Services” (Document Number: SC24 6001-00) which is available from International Business Machines at PO Box 29570, IBM Publications, Raleigh, N.C. 276260570 or on the WWW at www.IBM.com/shop/publications/order.
It is also possible for a user application on a z/VM virtual machine to communicate with another application via a tangible LAN, using Internet Protocol. This other application can be running on the same or different z/VM base portion or running on another computer system with a different type of operating system altogether. To support this communication, a tangible network interface card (“NIC”) is provided between the z/VM base portion and the tangible LAN. Previously known device driver software is provided to interface between the z/VM base portion and a subset of I/O devices within the tangible NIC. The tangible NIC provides all functions required for establishing an IP connection, and transferring data over the IP connection, i.e. (a) configuring the network interface, (b) starting the network interface, (c) sending a datagram from the device driver to the network, (d) sending a datagram from the network to the device driver, and (e) stopping the network interface.
To make the interface available for data transfer, the guest operating system (or the application) must instruct the device driver to configure and start the network interface for a specific, tangible NIC. When the application has data to send to an IP destination that is accessible via this network interface, it provides a datagram to the device driver. The datagram is a TCP/IP request or response, which includes application data and an IP destination address to identify the intended target on the network. The device driver inserts a device-specific header before the datagram to describe the IP destination address and any options relevant to the device. For example, one field in the header may indicate whether this is a unicast, multicast, or broadcast datagram. The device driver also notifies the NIC where the datagram is located in storage. When the tangible NIC is an OSA Express (“OSA-E”) adapter in Queued Direct Input/Output (QDIO) mode, the device driver follows the rules of QDIO architecture to interact with the tangible NIC. According to QDIO architecture, the device driver stores the datagram in an output buffer, updates the state of the output buffer, and executes an instruction to signal the tangible NIC that data is ready to send to the network. The tangible NIC retrieves the datagrams from storage and obtains the IP destination address from the header. Next, the tangible NIC uses an internal cache table to correlate the IP destination address from the header with a Media Access Control (“MAC”) address which identifies a destination on the tangible LAN. A cache table is maintained by each tangible NIC to record IP and MAC address associations detected on the tangible LAN (when furnished by other devices). Then, the tangible NIC sends the datagram on the tangible LAN to the destination, tangible NIC (or to multiple destinations in the case of a multicast or broadcast datagram). The datagram arrives at the destination, tangible NIC, where it is installed in storage owned by the target virtual machine. When the tangible NIC is an OSA Express in QDIO mode, the destination NIC installs the datagram in an input buffer, updates the state of the input buffer, and (if necessary) generates a I/O Interruption to signal the device driver that data is ready to send to the application. The destination device driver strips the device-specific header from the data and delivers the datagram to the target application.
US patent application entitled “Virtual Machine Operating System LAN” filed Jul. 16, 2002 by Macchiano et al., Ser. No. 10/197,306 discloses prior art, virtual NICs for communication between different virtual machines having the same common base portion. These virtual NICs were part of IBM z/VM V4R3 operating system. Each virtual machine includes a device driver for the respective virtual NIC. The common base portion maintains a table of IP addresses by which each device driver addresses its respective virtual NIC and other, corresponding addresses by which the base portion addresses each virtual NIC. Each device driver is programmed to receive an IP datagram from its application and pass it to the respective virtual NIC using IP. The datagram includes an IP address of the other virtual, destination NIC and an indication that the other application should receive the datagram. The base portion is programmed to determine the other address of the other virtual, destination NIC based on the table, and transfer the datagram to a storage location associated with the other virtual, destination NIC or the other device driver.
Tangible network switches are also known to interconnect devices to a tangible LAN. Such a switch provides the ability for “nodes” (Network Connection Points) to send data to and receive data from other nodes. An example of a “node” is a physical computer or a base portion of a virtual machine operating system. In existing virtual router solutions, there is a router between adjacent LAN segments. Each node on a physical LAN separated by a router is considered to be on a separate LAN segment.
Another virtual machine operating system is currently available from VMware, Inc. of Palo Alto, Calif., and runs on a personal computer (“PC”). This operating system also includes a common base portion and user portions. The VMware (TM of VMware, Inc.) operating system includes (virtual) device driver programs which are associated with respective applications. The device driver programs also simulate respective, virtual network adapters to communicate between different virtual machines in the same system (i.e. having the same base portion of the virtual machine operating system). Different virtual machines having the same base portion use IP to communicate with each other. The virtual network adapter performs the following functions: (a) receive data from a virtual machine device driver and pass it to another virtual network adapter, (b) receive data from another virtual network adapter and pass it to a virtual machine device driver, and (c) pass data from one virtual machine device driver to another virtual machine device driver. By using the virtual network adapter, the VMware operating system supports communication between virtual machines in the same PC. The VMware operating system also supports communication between a virtual machine and a tangible network using a tangible network adapter card on the PC. The VMware virtual adapter model only provides Layer two (i.e. Link Layer) support, and no IP Layer support. Also, each VMware adapter is defined as a fully simulated adapter in a simulated internal network within the PC, or mapped directly to a tangible adapter in a tangible external network. Any virtual machine using a simulated adapter is isolated from the tangible external network unless another virtual machine, having both types of adapters, acts as a router between the simulated network and the tangible external network.
A prior art IBM z/VM 4.3.0 virtual machine operating system allowed virtual connection of a user virtual machine to an external, tangible LAN. The common base portion included a virtual LAN which interfaced to device drivers of the user virtual machines. A communication support virtual machine executed a TCP/IP for z/VM V4R3 application, and was the interface between the virtual LAN and the external, tangible LAN. The TCP/IP application performed the functions of attachment, coupling and IP routing to the tangible LAN. This was accomplished by dedicating communication devices to the communication support virtual machine which performed control functions. All tangible LAN communications to and from the user virtual machines passed through this communication support virtual machine. While this technique for interconnection to the tangible LAN was effective, it was encumbered by the need for the communication support virtual machine which passed all LAN communications to and from other, user virtual machines.
An object of the present invention is to provide an improved technique for IP communication between a user virtual machine and a tangible LAN or other network.